roots and radicals

**comet2000** · August 3rd 2008, 04:34 PM

Solve each equation. Round your answer to two places if necessary.
26. 1875=3a^4

32. 10.56=12.4(1-r)^20

i don't understand this two problems. the two problems are color colded.
i hope it is ok to post this two problems in this thread. if not, sorry.

**Simplicity** · August 4th 2008, 01:34 AM

Originally Posted by comet2000

Solve each equation. Round your answer to two places if necessary.
26. 1875=3a^4

32. 10.56=12.4(1-r)^20

i don't understand this two problems. the two problems are color colded.
i hope it is ok to post this two problems in this thread. if not, sorry.

1.
$1875 = 3a^4$
Divide both sides by 3:
$625 = a^4$
Do forth root on both sides:
$\sqrt[4] {625} = \sqrt[4] {a^4}$
$5 = a$

2.
$10.56 = 12.4(1-r)^{20}$
Divide both sides by 12.4:
$0.8516... = (1-r)^{20}$
Do twenty root on both sides:
$\sqrt[20] {0.8516...} = \sqrt[20] {(1-r)^{20}}$
$0.992... = 1-r$
Add r to both sides:
$0.992... + r= 1$
Take 0.992... away from both sides:
$r \approx 0.007999$

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